The present invention relates to a plastics container assembly and is particularly concerned with containers having a base and an upstanding side wall and which are usually generally cylindrical in form and suitable for the marketing and storage of fluid such as paint. Paint containers of plastics are well known and are usually discarded when their contents are exhausted. For this reason it is important that the containers should be capable of inexpensive manufacture and of a structure which alleviates leakage of the fluid. This is particularly so where containers are formed as an assembly from a tubular wall and a base which is fitted thereto. Being of plastics, containers of this latter type can absorb quite severe shock forces, for example if dropped, and in these circumstances it is important for the base to be connected to the side wall in a manner which provides a fluid seal that is likely to be maintained during the application of reasonable shock forces to the container. It is an object of the present invention to provide a plastics container assembly having an upstanding side wall and a base fitted thereto which is sealed in a manner that alleviates leakage of fluid from the container when the container is subjected to reasonable shock forces and in which the fitting of the base to the side wall can be achieved relatively inexpensively and simply.